


Just A Theory...

by MK (Mari_Keiyou)



Category: Undertale (Video Game)
Genre: Alternate Universe - Underswap, Drug Use, Fluff and Angst, Multi, Post-Undertale Neutral Route - Near Genocide Ending, Questionable party
Language: English
Status: Completed
Published: 2017-02-02
Updated: 2017-02-02
Packaged: 2018-09-21 11:11:37
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,228
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/9546323
Author URL: https://archiveofourown.org/users/Mari_Keiyou/pseuds/MK
Summary: After losing everything closest to him and no signs that things would change for the better Paps had nearly given up... until someone  showed up out of the "blue" one day.





	

_“C’mon, don’t freak out, don’t freak out... he’s dead... you know this...”_

Papyrus kept willing himself to not panic as he stole glances at the shorter skeleton sitting next to him. In every other sense he’d swear up and down that this was his brother... only it wasn’t.

It couldn’t be...

That thing in human skin saw to that.

It only pretended to care, wearing a smile so deep that it rivaled his younger brothers and hid the fact that it had harbored murderous intentions with them... or at least, just with his brother.

And after a time he’d also found out the man behind the door was another that had fallen victim to this pretend human.

The nasty thing had the nerve to parade around the underground like it hadn’t done anything wrong, greeting other monsters and sparing them, as if it’s only objective was to deliberately rip away anyone close to him.

And it succeeded, killing the former queen and leaving to never come back... talk about a triple insult.

So he was convinced that this could not be Sans, it was some hallucination.

It had to be.

Mostly because this Sans was nothing like his brother, behaving more like himself, right down to the slouched posture and the carefree way he dressed... it was scarily reminiscent to himself, except for the magic...

..the magic.

It was blue, no doubt; another mark that should have signified that this was his younger bro, but it’s spark behaved much like his own orange flow.

Darker... aged.

So... he’d hallucinated a version of himself? Shorter? With his brother’s features?

It... it didn’t make any sense.

It was almost as if whatever universe this Sans was from just...

..swapped places.

Papyrus had questions, but he still wanted to remain casual since this other ‘him’ didn’t look much like he gave a rats ass that he just walked in unannounced and crashed on the sofa like he owned the place.

Besides, Papyrus was too stoned out of his mind to react to anything his overactive thought process was demanding to be rectified.

“hey” The other him suddenly spoke up, crack in his voice like he hadn’t spoken much.

“...Sup?” Pap offered casually.

“you gonna finish that stick?”

Paps looked down at the ashtray in his lap and gave it a thoughtful stare, most of a rolled joint still sat untouched at the bottom. He’d already smoked the other four earlier and he was still aware enough to know anymore would probably send him napping, and the last thing he wanted was to fall asleep in front of this new entity.

It might disappear...

He shrugged and gingerly handed the ashtray and his lighter over. “Knock yourself out, bud.”

“thanks.”

Papyrus half expected his lighter and tray to just hit the couch and prove he was just seeing things, but the objects made solid contact.

Gods... He was real.

Tired white orbs looked up at him and the skeleton cracked a smile. “oh good, for a while i thought that maybe...” He picked the stick out of the tray and sighed. “then again the papyrus i know woulda never used one of these...you could have just been something i made up out of desperation.”

Paps watched him in silence as he stuck the rolled cig passed his teeth and flicked the lighter on, drawing in a deep breath and letting smoke roll out in waves, like he’d done this sort of thing a million times.

Paps reached out a hand and touched the smaller skeleton’s shoulder.

“what’s up? did you think i was a hallucination too?”

This skele-no; this Sans sounded so tired... like he was about to cry, like he had been the one carrying the burden that had been placed on him as the first born, like he’d just lost everyone closest to him, like everything that ever mattered once upon a time meant nothing anymore...

Yet he wore the face of his brother...

Paps couldn’t take it, he leaned over and hugged this smaller version of himself.

The blue coated skeleton’s shoulders shook and when this Sans hugged him back, Paps couldn’t stop sobbing with him.

\---

Papyrus eventually grew accustomed to visits from his shorter alternate self whenever it was obvious the blue him needed to get away from whatever haunt plagued his time-line.

Paps already knew what that ‘something’ was, but he never brought it up. Instead he indulged the smaller skeleton with junk food, tv show re-runs, and many different forms of escape via alcohol and drugs.

This time, however; he had something else in mind.

“y’know, we could just shortcut to wherever this party is...” Sans spoke up, interrupting Pap’s thoughts. The two skeletons were trudging along a beaten path in Waterfall, on the way to Paps decided change in routine.

“Yeah we could, but what’s the harm in a little walk?” Paps shrugged.

“maybe nothing, but we’re pretty far out in the sticks, this is way past the blook farm.”

“We’re not going to get lost, I got directions from Mettsy” Paps said, fishing out a small map. “And according to him the guy hosting the party is an old friend, so it’s legit.”

“heh, if mettablook says it’s good then it’s good i guess.” Sans replied, still finding it hilarious that the Mettaton in this time-line was not only still a ghost, but also an under the table drug dealer. It made him wonder what Napstablook back in his dimension did in their spare time.

“Of course,” Paps said with a confident lilt in his tone. “He’s my buddy, he’d never lead me astray.”

\----

“I think I see a light up ahead.” Paps pointed out after some time. “Past that dead tree.”

“finally.” Sans sighed. “did mettsy say what kind of stock they’re packing or is it a surprise?”

“Honestly he said it was on a hush-hush basis.” Paps admitted, holding up a hand to pause Sans from speaking when the stocky skeleton looked back at him like he was ready to suggest they turn around.

“Before you say anything, most parties like this are kept on the down low since Undyne- I mean _“The Empress”_ declared some specific stuff to be illegal, all I know is that it’s a party.” He dropped his hands into his hoodie pouch and smiled a little.”Besides I figured something like this would be a nice change.”

Sans shook his head, a small grimace accompanying his usual impish grin. “...and did he say for certain this was one of the kinds of places monsters just go to hang and not just disappear at?”

“The only ones that do the disappearing are the ghosts, and they come back just fine.” Paps cocked an eyebone. “You’re not paranoid are you?”

“of course not; just _ribbing_ ya, pal.” Sans chuckled.

Paps laughed into his hand over the pun and sighed. “Ah, a classic.”

\----

As the two made it to the building it looked like it was less of a shack and more just a house in the middle of the wooded swamp. The lights were a bit dim but it didn’t look like the seedy joint that either of them had expected.

Especially since there was a rather buff looking monster seated on the porch, wearing sunglasses despite the fact that it was dark.

“a bouncer?” Sans pondered out loud.

“Maybe for the rabble rousers?” Paps suggested as they stepped up.

The monster stood up slowly and looked between the both of them. “You two here together?”

Paps nodded, a bead of sweat dotted his head. “That’s right. I even have the G to get in.”

The guard wrote something on a clip board and shook his head. “You don’t give that to me, there’s someone inside who takes the G.” The monster grinned and handed a piece of paper to Paps. “This is the list of rules you’re required to follow, break e’m and I break you, understood?”

“crystal.” Sans replied.

The monster stepped out of the way and settled back into his recliner. “Behave in there or I’ll hear about it.”

They stepped in and the first thing that hit them was how many people had actually shown up, and it looked like the two arrived just in time because there were still monsters in the foyer removing coats.

“i think i’m gonna keep mine on.” Sans said as both he and Paps stepped into the room to get a better look at their surroundings and possibly find the monster taking the money. “what’s on that paper?”

Paps briefly looked the sheet over before stuffing it in his pocket. “Just the usual ‘what happens in the drug den stays in the drug den’ mantra, not a big deal.”

“gotcha.”

After they found the monster in charge of the party the two walked into a bigger room where most of the guests mingled, the music from the small stereo playing a slow remix.

“Let’s find a place to sit before we get wasted, sound good?” He pointed at a plush couch up against a wall, occupied by only one other monster.

Sans nodded. “sounds like my kinda plan.”

As the two made their way to the couch they could tell their seat mate had already been here early on since it took the haggard blue rabbit more than a few seconds to realize he’d been joined on the couch.

“Yo, ain’t you two those sentries they stuck at the ruins in snowdin?”

Sans pulled his hood over his head as Papyrus spoke up. “I am, but this one isn’t.”

The rabbit squinted at them and laughed a little. “Eh, whatever it’s not my business.” He gestured to the table with a yawn. “I got a little more than I actually needed so help yourself.”

Sans looked at the bag on the table and by the color of the contents inside he wasn’t exactly certain it was a brand he’d ever consider, but if it meant he didn’t have to get up again to check out what was at the selling table right away..

“don’t look a gyftrot in the mouth as they say..” He muttered and helped himself to a pre-rolled stick.

“I hear ya there, bud.” Paps said grabbing one himself.

\---

“-cough- yeah, i think this goes up there in the ranks of ‘what the hell did i just smoke’.” Sans said with a curt laugh.

The effects from the blunts had hit the two skeletons a bit quicker than either had anticipated. Whatever was in this one was sweet but had the slightest hint of vegetable, not surprising since it was the rabbit that bought them, but said rabbit had gotten up to speak to someone else and hadn’t come back so both assumed he’d left.

“Y-yeah no kiddin’.” Paps agreed. “It tastes like the back room of a farmers market.. kinda making me sick.” Instead of finishing off his roll he crushed it into the ashtray. “Maybe it’d be better if we leave the rest of that guy’s stash to himself, I’ll go see if I can’t find us something a little more-!”

Sans caught the hitch in Pap’s words and glanced up at his tall friend. “sup, stretch?”

Papyrus wasn’t sure if it was the drugs messing with his head, but as he got up to make good on his intent to get them something else he noticed two things. One, the lights in the room had been dimmed . second and most jarring of his discovery, half of the people in the room were all occupied in their own spaces and...

And just openly making out.

Even in the low lighting it was obvious that some were going so far as heavy petting, without a care as to who could be witnessing.

Paps shook his head and sat back down. “Y’know what, never mind this stuff is fine enough.”

Sans gave Paps a quizzical look before kneeling up on the couch to get a better look of the room and his face bloomed a brilliant blue before he sank back onto the couch. “welp, this is awkward.”

“I hope whatever is in these drugs isn’t inciting that ..” Paps said, his own face a bit of an orange flush.

A look of abstract fear crossed Sans’s face and the lights in his eyes all but vanished. “if that’s the case i’m not having anything more from here.”

Both sat in the couch not saying anything for a few moments, but neither had any inkling to suddenly race off and find a monster to flirt with and they sighed in relief.

“Okay, it’s not drug induced... still doesn’t explain what’s got everyone so damn horny in here.”

“cozy atmosphere, everyone’s got a good high going... so i guess if ya don’t care why the hell not.” Sans offered, picking at the string on his hoodie.

“Do you?”

Sans blinked, eyelights flashing a tad wider than usual when he looked at Paps. “uh, what’s that?!”

“I was asking if you wanted to leave, you don’t look too relaxed right now, bud.”

Sans opened his mouth to speak but a slinky looking monster in a low draped one piece strolled up and sat between the two, smiling wickedly at them.

“Hey boys, you look like you could use a bit of company..” She slid rather long arms around the both of them as she continued speaking. “I’ve got a friend that’ll be around soon if either of you feel like a bit of-”

“Actually, we’re just here together!” Paps spoke up suddenly.

The monster frowned a little. “Oh darn then.. didn’t mean to interrupt, I suppose I’ll follow the rules and leave you both be.” Another arm both hadn’t noticed snagged the baggie off the table and she sauntered away with a wink.

“rules...” Sans muttered and without asking he reached over and pulled the paper out of Pap’s hoodie.

“Hey-”

San’s eyelights scanned the sheet and he blinked a few times before speaking “.... Paps, how thoroughly did you read this thing?”

Paps scratched the back of his skull. “I uh, skimmed the first few lines, why?”

Sans chuckled and passed the paper back to him. “pal, we’re at a make out party.”

“We’re _what?!_ ” Paps looked at more of the words and slapped a bony hand to his forehead, wishing the couch would just eat him whole “Oh gods, Sans I’m so sorry, this was suppose to just be a party not a friggen- dammit Mettablook...”

“s’fine paps, really.” Sans sat up and patted him on the shoulder. “listen i’m gonna go see what’s at that table and grab us a few good lights and drinks, we’ll just tell people we aren’t interested if we get approached again and it’ll be fine.”

Paps thought it a bit silly to stick around at a party that neither of them had any plans on participating in, but he was curious about what kind of goods might be available, so he nodded. “Alright, it’s your call, we’ll leave whenever you’re ready.”

“you’re the one who said not to worry, remember? we can still have a good time.”

\---

“an-and then she’s all like ‘what are you crazy, it’s purple now!”

Paps was laughing, but in that same moment something fleeting crossed his mind that seemed...

Tempting.

It wasn’t something he’d consider sober, and common sense would have agreed if it weren’t also as stoned as he was, but the more the two of them sat at their corner couch laughing about nonsensical stuff the more he was reconsidering not participating in the party.

Not that he wanted to wander away and find some willing party goer, no; his interest was in fact aimed at the one guy he’d brought here to cheer up.

Paps face felt hot as the thought overstayed it’s welcome and he shook his head. ‘the fuck am I even thinking?! there’s no way he would-’

“so, something on your mind pal?”

Breaking Pap’s thoughts, the tall skelly looked up to see Sans handing him back the blunt he’d taken from Paps.

‘Oh, maybe that was why...’ Paps continued to think as he took back the roll.

Earlier on Sans had come back with a multitude of goodies and at some point after a couple drinks and smokes the two of them had just started rolling one and sharing the same stick, and after Pap’s handed one he’d rolled to Sans for what seemed like the hundredth time before his wild thought took over he had paid closer attention as Sans slipped the blunt between his teeth. There was something about the way the smaller skeleton just breathed in the chemicals, the way he closed his eyes, chest rising up as he took a deep breath and let the vapors roll slowly out with a soft sigh...

The sight of him, it made Pap’s soul lurch and his mind went went toward wondering... just wondering.

Sans was laughing and it brought Paps back from his thoughts again. “Whaz so funny?”

“heh, you dude.” Sans was laughing so hard he hunched over clutching his middle. “your whole face looks like a frigging orange creamsicle, it’s hilarious.”

Oh, he was blushing. He took a sharp hit and sat it on the ashtray. “H-hey, mind if I ask you something?”

Sans wiped tears of laughter out of his eyes. “what’s up?”

“It’s nothi’n big, just about, y’know; that day you just showed up outta the blue- Heh, ‘sfunny cause you got blue magic-”

“...”  
“...”

Both skeletons laughed so hard about this obvious revelation that they wound up on the floor in front of the couch, the music mixed in with the sounds of the other patrons somewhat drowning out how loud the two had actually gotten.

After they stopped to catch their breaths Paps looked around again and in that new point of view he could see the monster that had accosted them earlier with another and the dress that she had been in was nowhere to be seen.

Paps gulped and stood up quickly... only to feel himself falling down again, this time towards the table.

“oh damn, Paps!” He heard Sans call out and he felt two arms snake around his middle and pull him away from the table and back onto the sofa.

A few grunts and shifts later Paps’s vision reoriented and he found himself looking down at Sans, who for all the world looked like he’d run a marathon, flushed and panting heavily from their tumble, perfectly centered under him.

Pap’s drug addled thoughts wandered once again.

Their knees knocked as Sans tried to sit up but Paps unwillingness to let him move much only sent him lying back down.

“y-you okay, that was a close one eh?” Sans blinked, his vision had fuzzed a bit but there was no mistaking that the taller skeleton had something to say. “s-something the matter? you ain’t hurt are ya?”

Paps moved his teeth up and down like he was working up the nerve to speak, the he gulped audibly and spoke so fast that it was nearly impossible to make out in the din.

So nearly in fact that Sans was certain he’d heard right, but he had to ask again. “what was that you said?”

“I asked- I asked if it was okay for me to-to kiss you.”

He had heard right. Sans could feel his face heat up and his soul vibrate against his rib cage, he had to will himself to not shake from the adrenaline rushing through his bones.

So much for just wanting to chill.

He was already resigned to the idea that this tall version of himself couldn’t possibly be the type to ask such a question, since he himself had spent the better part of a week accidentally falling for the lanky sack of bones and another willing himself to let go of any idea that the other would even consider reciprocating those feelings back.

But...if he was hearing right and it wasn’t the drugs talking...

“wh-why would you want to do that?” Sans asked anyway, silently hoping it wouldn’t change Paps mind.

Pap’s sighed. “I just... I’m curious, aren’t you?”

Well, not quite what he’d hoped to hear, but he decided to indulge the skell, relaxing into the seat of the couch with a smile tugging the corners of his mouth. “curious? what do ya mean?”

“Just-’s just a theory I want to try- for fun, ya know.” Paps stammered, making things up as he tried to write off his embarrassment. “S-since my magic’s orange, but yours is blue- and if we’re suppose to be the same people from alternate universes then how would us kis- I mean it’s probably something easily explained if we tried something besides this-but we’re are at a party where everyone is kissing already so this is the kind of place we should-Oh gods that sounded wrong, I mean-!!”

Sans tugged at the collar of Pap’s hoodie and used it as leverage to lean up and silence the babbling skeleton with a clank.

\---

Mettablook hadn’t been planning to go to that party, places like this were more Napstabot’s thing. But he couldn’t contain his curiosity after he’d convinced his best friend and regular client that he should go to it and take his crush with him.

______**FLASHBACK-** _ _ _ _ _ _

_______‘I got this batch from the guy that speaks in hands on the river, it’s got this silvery color- Pappy is something the matter?’_ _ _ _ _ _ _

_________‘What? Oh, no... well only a little I guess.’_ _ _ _ _ _ _ _ _

___________‘Tell me then, I’m a good listener.’_ _ _ _ _ _ _ _ _ _ _

_____________‘...Well you see I- I’ve got this friend who told me that he... ah screw it; you know that guy who’s been coming over to my place?’_ _ _ _ _ _ _ _ _ _ _ _ _

_______________‘You mean the one that looks like your-Oh! I’m sorry... that’s probably a sore spot for you-’_ _ _ _ _ _ _ _ _ _ _ _ _ _ _

_________________‘No, that’s not it... No, he’s nothing like my bro at all... and that’s the problem.’_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

___________________‘Why would he be a problem? Are you not getting along?’_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

_____________________‘We get along fine...'_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

_______________________‘... Ohhh wait I get it, you’re pining for the little guy aren’t you?’_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

_________________________‘Pffft, pining?! .... no you’re right. Fuck, what should I do? I don’t want to scare him off.’_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

___________________________‘If you ask me, staying cooped up in Snowdin is probably giving you two cabin fever... tell you what; I have this friend that’s hosting a party...’_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

______****______________________**FLASHBACK END-** _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ** ** _ _ _ _ _ _

Mettablook was still congratulating himself for cleverly getting Papyrus out and about, knowing full well that if the lanky skeleton kept continuing with his usual routine of teleporting to his farm and just going home that it would break him...

Most of all though, he’d blessed the stars when the other showed up to break the tandem.

At first when Paps had stopped by with the smaller skeleton in tow Mettablook almost fell through the floor in shock, believing it to be Paps younger brother back from the dead.

It was definitely not him though, looks aside he was just as forlorn and haggard as Paps was, if not to the point of mirrored.

Mettablook could see that it was what Paps needed though, and when the tall skeleton confessed that he more than liked this blue hooded skeleton he knew it would be up to him to give that extra push.

Then again an open make out party with drugs might have been an over the top push as he already hovered past a few guests who were not so subtly doing more than just making out in the more darkened rooms.

“Oh, maybe this wasn’t my brightest idea..” Mettablook said to himself as he floated away from the rooms and headed towards the supply table.

“Ah, Mettsy!” Said a voice by the table.

“Felix, how’s the party?” Mettablook said, setting his backpack onto the table.

“Going full swing, only had to break up one fight earlier.”

“Oh- w-well better than two or three.” Mettablook replied, hoping it wasn’t the skeletons.

“There were a few I was going to speak to since they looked baffled but I guess some people just need time to settle into the idea first, like those guys over in the den for instance.”

Mettablook glanced to the direction Felix pointed and sure enough there they were, from where he hovered he could see the skeletons locking teeth and a sheen of blue and orange as magic tongues dancing off one another.

Mettablook made a noise of giddiness and Felix cocked an eyebrow at the pink ghost. “Y’know it’s not polite to stare, little buddy.”

“Oh, you’re right, sorry. You see that guy over there is someone I was specifically hoping-”

“Uh, I think he’s staring at you.”

“What?!” Mettablook looked back over and it was true, a fixed orange iris was trained on him and it made Mettablook feel like he was suddenly being judged for every awful thing he’d done, it made his back shiver in fear.

Suddenly Paps looked back down at the other skeleton, leaned in and looked like he was whispering something that made the smaller one laugh and with a pop the two vanished out of sight.

“I know a death glare when I see one.” Felix laughed. “Skull guy might blast you into the next world.”

“Maybe right now he’d think about it, but I know he’ll just thank me later.”

-FIN- 

**Author's Note:**

> This was a nightmare to edit X_X
> 
> Any future writings with this pair might be shorter and more to the point.


End file.
